September 06, 2019

Air disinfection in measles transmission hotspots

Measles is the most contagious airborne infection. The long-term solution to the increasingly common outbreaks of measles is to re-establish herd immunity through vaccination. Although immunisation is the optimal approach to preventing measles, upper-room germicidal ultraviolet (GUV) air disinfection, a readily available environmental intervention with proven efficacy, should be used in selected paediatric waiting rooms, school classrooms, cafeterias, and other group settings that are key sites of transmission.

GUV air disinfection works by rapidly disinfecting upper-room air, which continuously then exchanges with contaminated lower-room air, resulting in highly cost-effective protection for room occupants.

Before immunisations were available for common childhood respiratory viruses, and antibiotics for tuberculosis, shielded, upper-room GUV fixtures were widely distributed to reduce airborne transmission in schools, hospitals, and other congregate settings.

Between 1937 and 1941, Wells and colleagues studied the efficacy of upper-room GUV to control measles in classrooms in two schools in suburban Philadelphia, PA, USA. The average infection rate was 53·6% among more resistant, older children (grades 5–12) in classrooms without GUV air disinfection, compared with the average infection rate of 13·3% among more susceptible, younger children (grades K-4) in classrooms with GUV air disinfection (appendix).

However, when GUV air disinfection was distributed to schools in rural upstate New York, NY, USA and in urban London, UK there was no protective effect. In both locations GUV air disinfection was installed in classrooms and common areas, but unlike in suburban Philadelphia, children rode home on school buses in rural upstate New York and played together in crowded tenements in urban London.

The important lesson learned was that environmental controls are only effective when they target the principal sites of transmission. The application of upper-room GUV air disinfection is better understood now than it was 80 years ago, and the safety of properly designed fixtures is well established. It is currently widely used in high-risk health-care facilities to prevent tuberculosis transmission, where 80% efficacy has been shown. It is also effective against airborne influenza.

GUV uses UV-C, which penetrates skin poorly and poses minimal risk for skin cancer and cataracts compared with the more penetrating and dangerous UV of sunlight. Even brief exposure to intense sunlight far exceeds the 8 h UV limits for lower-room GUV exposure. Accidental overexposure to direct GUV in the upper room by painters or cleaners causes temporary eye or skin irritation, but no lasting effects.

Comments

Measles is the most contagious airborne infection. The long-term solution to the increasingly common outbreaks of measles is to re-establish herd immunity through vaccination. Although immunisation is the optimal approach to preventing measles, upper-room germicidal ultraviolet (GUV) air disinfection, a readily available environmental intervention with proven efficacy, should be used in selected paediatric waiting rooms, school classrooms, cafeterias, and other group settings that are key sites of transmission.

GUV air disinfection works by rapidly disinfecting upper-room air, which continuously then exchanges with contaminated lower-room air, resulting in highly cost-effective protection for room occupants.

Before immunisations were available for common childhood respiratory viruses, and antibiotics for tuberculosis, shielded, upper-room GUV fixtures were widely distributed to reduce airborne transmission in schools, hospitals, and other congregate settings.

Between 1937 and 1941, Wells and colleagues studied the efficacy of upper-room GUV to control measles in classrooms in two schools in suburban Philadelphia, PA, USA. The average infection rate was 53·6% among more resistant, older children (grades 5–12) in classrooms without GUV air disinfection, compared with the average infection rate of 13·3% among more susceptible, younger children (grades K-4) in classrooms with GUV air disinfection (appendix).

However, when GUV air disinfection was distributed to schools in rural upstate New York, NY, USA and in urban London, UK there was no protective effect. In both locations GUV air disinfection was installed in classrooms and common areas, but unlike in suburban Philadelphia, children rode home on school buses in rural upstate New York and played together in crowded tenements in urban London.

The important lesson learned was that environmental controls are only effective when they target the principal sites of transmission. The application of upper-room GUV air disinfection is better understood now than it was 80 years ago, and the safety of properly designed fixtures is well established. It is currently widely used in high-risk health-care facilities to prevent tuberculosis transmission, where 80% efficacy has been shown. It is also effective against airborne influenza.

GUV uses UV-C, which penetrates skin poorly and poses minimal risk for skin cancer and cataracts compared with the more penetrating and dangerous UV of sunlight. Even brief exposure to intense sunlight far exceeds the 8 h UV limits for lower-room GUV exposure. Accidental overexposure to direct GUV in the upper room by painters or cleaners causes temporary eye or skin irritation, but no lasting effects.